A series of AB(3)/PANI composites were prepared by adding polyaniline (PANI) into La0.7Mg0.25Ti0.05Ni2.975Co0.525 (AB(3)) hydrogen storage alloy, which was prepared by magnetic levitation melting, and the composites were investigated by XRD and SEM. The effects of PANI concentration on the hydrogen absorption-desorption properties and discharge capacities of AB(3) alloy were systematically studied by P-C-T isotherms and LAND battery test system, respectively. The results indicated that the addition of PANI did not change the hydrogen absorption capacity of AB(3) alloy distinctly, while the hydrogen desorption plateau pressure of AB(3) alloy decreased firstly, and then increased with the increase in the PANI concentration, the minimum plateau pressures of 0.022, 0.1, 0.321 and 0.55 MPa were obtained with PANI concentration of 2 wt% at 25, 50, 80 and 100 degrees C, respectively. It was theoretically verified by the changes in enthalpy and entropy of AB(3)/PANI hydrides dehydrogenation which were calculated by Van't Hoff equation. In the present paper, the phenomenon that PANI improved the hydrogen absorption kinetics of AB(3) alloy was found; the influence of PANI concentration on hydrogen absorption kinetics of AB(3) alloy was more apparent at higher temperature. The activation energies of dissolved hydrogen in AB(3)/PANI hydrides were calculated from hydrogen absorption kinetics and the Arrhenius equation. LAND experiments demonstrated that, the AB(3)/PANI electrodes composites possessed higher cycling discharge capacity retention rates than AB(3) electrode alloy. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.